1. Field of the Invention
The present invention relates to a circuit device, especially to a circuit device in which a hybrid integrated circuit built on an upper surface of a circuit board is sealed by use of a case member.
2. Description of the Related Art
By referring to FIG. 7, a configuration of a hybrid integrated circuit device 150 in which a case member 111 is employed will be described. Firstly, on a rectangular surface of a substrate 101, a conductive pattern 103 is formed with an insulating layer 102 in between, and a circuit element is fixed at an intended position on the conductive pattern 103 so as to form a desired electric circuit. Here, a semiconductor element 105A and a chip element 105B serving as circuit elements are connected to the conductive pattern 103. A lead 104 is connected to a pad 109 composed of the conductive pattern 103 formed in a peripheral part of the substrate 101, and functions as an external terminal. A sealing resin 108 has a function of sealing the electric circuit formed on the surface of the substrate 101.
The case member 111 has a substantially frame-like shape, and is in contact with side surfaces of the substrate 101. Furthermore, in order to secure a space for sealing on the upper part of the substrate 101, an upper end part of the case member 111 is located above the upper surface of the substrate 101. Then, a space above the substrate 101 and surrounded by the case member 111 is filled with the sealing resin 108. Thus, circuit elements, such as a semiconductor element, are sealed by the sealing resin 108. In such a configuration, even if the substrate 101 is relatively large, it is possible to seal circuit elements incorporated on the supper surface of the substrate 101 in resin sealing by filling the sealing resin 108 into the space surrounded by the case member 111 and the like.
This technology is described for instance in Japanese Patent Application Publication No. 2007-036014.
However, the above-described hybrid integrated circuit device 150 has a problem that warpage occurs in the case member 111. To be more specific, referring to FIG. 8A, the case member 111 used for resin sealing is required to have a substantially frame-like shape when viewed from above.
However, each side wall part of the case member 111 formed by injection molding of a thermoplastic resin or the like warps inwardly (refer to FIG. 8B). If the side wall parts of the case member 111 are deformed and warp inwardly in such a manner, this phenomenon makes it difficult to seal the upper surface of the substrate by use of the case member 111.
As for the occurrence of warpage in the case member 111 as described above, the following reasons are conceivable. Specifically, such conceivable reasons include: that the thickness of the case member 11 is uneven; that the temperature of a mold for injection molding of the case member 111 is uneven; that pressure inside of the mold cavity is uneven; that a filler and the like contained in a resin constituting the case member 111 is anisotropic; and the like.